‘Tombstoning’, also known as Drawbridge effect or Manhattan Skyline effect, is considered a common defect in surface mounting technology. ‘Tombstoning’, i.e., a phenomenon where electronic components erect like tombstones, is due to unbalanced surface tension of two soldered end portions of an electronic component. Particularly, when a low mass chip-type electronic component is soldered on a substrate such as a printed circuit board, the unbalanced surface tension may easily occur and draw one soldered end portion to the substrate and the other soldered end portion free, thus causing ‘tombstoning’.
Generally, the unbalanced surface tension of two soldered end portions occurs due to poor soldering pad design, non-uniform heating of soldering surfaces, low reactivity of solder, non-uniform application of solder and so on.
With the current trend toward miniaturization of electronic devices there is a concomitant trend toward reducing the size of the electronic components themselves. The reduction in size and mass of electronic components has been a significant aid in the miniaturization process but has created problems such as ‘tombstoning’. Referring to FIG. 9 and FIG. 10, such a typical electronic component 10 is prone to tombstoning on a printed circuit board 12 due to unbalanced surface tension of two soldered end portions. ‘Tombstoning’ can cause electric connections between the electronic component and circuits to be broken, resulting in the electronic component losing its functions and causing a mounting failure.
What is needed, therefore, is a surface mounted electronic component having ability of avoiding ‘tombstoning’.